Tube and shaft finning machines

ABSTRACT

A machine for winding fin onto tubes comprises a bed having a headstock through which passes a retractable mandrel for supporting a first tube. A saddle which traverses the bed carries a strip guide, a guillotine and a welding torch. Strip is wound from one tube to a second aligned with the first, the strip is welded to the two tubes and then severed, the first tube removed, and the second tube returns with the saddle to the position occupied by the first tube.

United States Patent [1 1 Norris Nov. 20, 1973 TUBE AND SHAFT FINNING MACHINES,

[76] Inventor: Douglas C. Norris, 6 Savilles Cl.,

Eaton Socon, England [22] Filed: Sept. 17, 1971 [21] Appl. No.: 181,542

[30] Foreign Application Priority Data Sept. 22, 1970 Great Britain 45,165/70 [52] US. Cl 228/5, 29/157.3 AH, 29/202, 228/ l 5 [51] Int. Cl B23k 1/20 [58] Field of Search 29/33, 157.3 AH,

29/202 R, 202 D, 477.3; 113/1 C, 118 A; 228/5, 15, 17; 93/80, 81; 219/6, 62

[56] References Cited UNITED STATES PATENTS 3,485,116 12/1969 Fender..'.. 29/l57.3 AH

3,427,427 2/1969 Rudd 29/ 157.3 AI-l 3,262,624 7/1966 Benteler et al. 228/ 17 2,178,671 11/1939 Osborn 113/1 C 2,174,928 10/1939 Riemenschneider et al 113/1 C 2,004,387 6/1935 Dewald 29/157.3 AH 1,830,357 1l/193l Gortner 113/1 C FOREIGN PATENTS OR APPLICATIONS 989,785 4/1965 Great Britain 113/1 C 235,114 8/1964 Austria 113/1 C Primary ExaminerRobert D. Baldwin Assistant ExaminerRobert J. Craig AttorneyC. Yardley Chittick et al.

[5 7 ABSTRACT A machine for winding fin onto tubes comprises a bed having a headstock through which passes a retractable mandrel for supporting a first tube. A saddle which traverses the bed carries a strip guide, a guillotine and a welding torch. Strip is wound from one tube to a second aligned with the first, the strip is welded to the two tribes and then severed, the first tube removed, and the second tube returns with the saddle to the position occupied by the first tube.

21 Claims, 12 Drawing Figures PATENTEU HUV 2 0 I975 SHFFT 30F 3 Fig.12

TUBE AND SHAFT FINNING MACHINES BACKGROUND OF THE INVENTION Tubing of circular, oval and other cross-sections, bearing a helical fin on its outer surface is used a great deal to conduct hot gases and liquids. In the automobile field, recent concern over air pollution has led to the development of devices for controlling the content of exhaust gases. In one such device the gases are fed before being discharged through a finned reactor operating at high temperatures. So that it may have a relatively large cross-sectional area but be of relatively low overall height consistent with the space available to it, the reactor preferably has a casing formed from tubing of oval or other non-circular cross section. Mild steel has been found to have disadvantages when used for the casings of such reactors and it is now preferred for such casings to be made from stainless steel.

The winding of continuous fins onto thin walled tubes presents certain difficulties when the mass-production of finned tubes is being contemplated. Thus, there are the problems of getting the fin started at the commencement of winding, securing the fin in place, and using a mandrel to support the thin wall of the tube against collapse while at the same time making provision for the quick removal of the tube once winding has been completed so that the operation may be recommenced using a fresh tube. In connection with the securing of helical flights to solid shafts, it is conventional to weld the fin to the shaft at intervals throughout its length but the known welding methods have proved unsatisfactory in connection with stainless steel tubing.

These problems are aggravated if the tubing is of non-circular curvilinear or partially curvilinear crosssection because the known methods of winding fins onto shafts of circular cross-section cannot be employed with tubing of sucn non-circular cross-section without the strip wrinkling and buckling.

A first object of the invention is therefore to provide a method for securing fins onto tubing having a crosssection which is circular, or non-circular but devoid of sharp corners, so as to materially increase the speed at which finned tubes can be produced.

In practising the invention to achieve this first object, a first tube is supported on a mandrel and a second tube is aligned axially with the first, the tubes are rotated so that a fin, secured to the first tube at its end remote from the second tube, is wound along the first tube and on to an end portion of the second tube, the fin is secured to end portions of both tubes by welding and severed to free one tube from the other, the mandrel is retracted to release the first tube, the second tube is advanced so as to occupy the position previously occupied by the first, and winding is recommenced. After the second tube has been advanced, and either before, after or simultaneously with, the recommencement of winding, a third tube may be located in the position occupied by the second tube before its advancement.

A finned tube produced by the method in accordance with the invention has a fin which is welded to the tube wall only at the ends of the tube. The length of fin between these end portions may be held in place by being indented into the tube during winding. By limiting the welded connections solely to the tube ends, the equipment required may be considerably simplified and the strip from which the fin is formed may be wound in the cold state.

Apparatus for performing the method of the invention may comprise means for supporting two tubes in axially aligned relationship, a strip guide for preventing wrinkling or buckling of the strip and setting the pitch of the fin being wound, the strip guide being traversable axially for the length of one of the tubes and for the length of at least an end portion of the other, means to enable said one tube to be released and the other tube to be advanced axially to take its place, and strip welding and severing means.

A preferred apparatus comprises a bed, a carriage movable along the bed and mounting a strip guide, a head stock and a tail stock, an intermediate support located between the head stock and tail stock, a mandrel extending between the head stock and intermediate support, the mandrel being retractable through the head stock, a feed device associated with the tail stock for advancing a tube supported between the intermediate support and tail stock into a position supported on the mandrel, and strip welding and severing equipment. The strip welding and severing equipment may be supported on the bed of the apparatus adjacent the intermediate support but is preferably mounted on the carriage.

A second object of the invention is to provide a method for winding and securing fins onto tubing which is of non-circular cross-section but devoid of sharp edges. To achieve this object, the strip intended to form the fin is fed through a guide which is maintained in a predetermined position relative to the peripheral surface of the tube so as to prevent wrinkling or buckling of the strip and to set the pitch of the fin being wound. Preferably, in addition to being traversable axially of the mandrel on which the tube is supported, the guide is movable in both directions perpendicular to the mandrel axis in order to maintain the necessary relationship between the guide and tube.

The guide may be in the form of a block provided with a groove, channel or slot through which the strip is fed or in the form of rollers between which the strip is fed.

Advantageously, when fin is being wound onto a curved part of the tube, or that part of the tube having the sharper curve, the strip is controlled both at the zone where actual bending takes place and at an ironing zone downstream of the bending zone.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a machine set up for winding fins onto oval tubes;

FIG. 2 is a view of the saddle taken on line 2-2 of FIG. 1;

FIG. 3 is a perspective view showing the construction of the strip guide for use in winding fins onto tubes of oval cross-section;

FIGS. 4 to 8 illustrate the steps performed by the machine shown in FIG. 1 when winding a fin onto a tube of oval, circular or other cross-section;

FIGS. 9 to 12 illustrate in a view looking axially of the mandrel the movements of the strip guide shown in FIG. 3 during the finning of a tube of oval crosssection.

DESCRIPTION OF PREFERRED EMBODIMENT However, those skilled in the art will appreciate that with-appropriate modifications, the machine can be made to fin tubes having a cross-section which is circular or non-circular but devoid of sharp edges, as well as solid shafts.

Referring to FIGS. 1 and 2, the machine comprises a bed 1 having a headstock 2 on which two drive motors, namely a low speed motor 3 and a high speed motor 4. A leadscrew 5 extends along the length of the bed and serves to traverse a saddle 8 along the bed in the direction away from the headstock. The saddle runs on antifriction bearings 7 and is prevented from lifting from the bed by a bar 71. The saddle is returned at high speed to .its position close to the bed by means of a pneumatic cylinder 72 mounted on a headstock and extension 10 of the bed and having a piston rod 73 connected to the bar '71. The extension has guideways for a wheeled trolley 11 which is movable along the length of the extension under the action of a hydraulic cylinder 12 housed in the bed. The bed is extended at the end remote from the headstock by an extension 13 on which is mounted a tailstock 14, the position of which is adjustable along the length of the extension 13.

A mandrel 15 extends through the headstock and has its headstock end supported by an upstanding bracket 16 on the trolley 11. With the mandrel in the position shown, i.e. where the trolley 11 is close up against the headstock, the other end of the mandrel is supported by an intermediate support or hearing steady 17.

A spindle 110 within the headstock mounts a wormwheel 111 which is driven by a wormgear 113 on a shaft provided with two pulleys 112 each of which is driven by way of-a belt from a respective one of the motors 3, 4. Each motor incorporates a clutch so that the shaft can be driven from either motor as required. The spindle is tubular and the mandrel passes through it and is driven by some suitable drive connection such as a dog clutch which is engagable when the mandrel is in its forward position or by splines on the mandrel which transmit drive in any longitudinal position of the mandrel.

The leadscrew is driven from the spindle by way of a gearing and clutch arrangement 6, the gear ratio being changed in accordance with the pitch of the fin to be wound. Unless the mandrel is non-circular, means such as a key or spline is provided positively to transmit the drive to a tube carried on the mandrel in order to avoid slip. In the case under discussion where the tube is oval, a mandrel of corresponding shape is employed and no auxiliary drive transmitting device is required. Although for thin walled tubes which are liable to collapse during finning a mandrel is essential, it may be omitted during finning stronger tubing or shafts providing other supports are provided.

Movement of the trolley 11 to the left as seen in FIG. 1 retracts the mandrel so as to bring its right-hand end within the spindle nose 18 of the head stock. A tube T1 carried on the mandrel is thereby released and can be removed manually or by automatic unloading means.

The tailstock l4supports a pneumatic cylinder 19, the piston rod of which is connected to a tube support head 20 slidable longitudinally of the bed on rods 201. The support head 20 carries a rotatable support or dolly 202 which engages within a second tube T2 aligned with the tube T1. Two cradles 203 are provided to support the tube T2 before the dolly has engaged it,

the cradles holding the tube at a level slightly below the working level illustrated.

Metal strip 5 is fed from a reel (not seen in the drawings but located on the left hand side of FIG. 2) to a strip guide 21 carried by the saddle and is wound into a helix on the tube Tl supported by the mandrel in consequence of the combined effect of rotation of the mandrel and traverse of the strip guide.

Referring now to FIGS. 2 and 3, the saddle 8 has a main body part 81 on which is rigidly secured a bush housing 82. The housing 82 has a cylindrical opening 83 in which a cylindrical bush 84 is rotatable in suitable bearings. The bush 84 has an opening 85 which corresponds in shape to the outer surface of the tube T1 to be finned. Mounted in front of the bush housing as viewed in FIGS. 2 and 3 are slideways 86 for a strip guide support slide 87 (omitted from FIG. 2) which is movable horizontally and vertically between the slideways 86. The strip guide 21 is mounted to pivot about a vertical axis on top of the support slide 87.

The body part 81 of the saddle has horizontal guideways extending in the direction normal to the axis of the mandrel, and serving to guide the movement of a cross slide 91. The slide has a frame 92 to which a pneumatic cylinder 93 is pivoted. The piston rod of the cylinder has a screw-threaded end portion which screws into a trunnion block 94 pivoted between a pair of spaced first arms 95 of a bell crank lever pivoted to the frame 92 and 96. The second arms 97 of the lever are articulated by a link 98 to a tail-end portion of the movable blade 99 of the guillotine 100 having a fixed blade 101. The blade 99 is pivoted between a pair of upstanding posts 102 which are joined at their upper ends to form a support for a slideway 103 which extends at an angle of 45 to the horizontal and lies in a vertical plane extending longitudinally of the bed. A pneumatic cylinder 108 is associated with the slide and is operable to advance and retract a welding torch 104 by a short distance, say three-fourths inch (1.87 cm). A shield, not shown in the drawing, covers the welding torch. The welding torch is associated with a finger 1 10 which, when the torch is operating, engages the junction between the fin and tube and controls the position of the electrode. A further cylinder 105 is operable to advance and retract the cross slide 91. First and second limit switches 106, 107 arranged on the bed are actuated by a finger 108 projecting from the body of the saddle.

A control system 9 is provided for automatically controlling the machine, and is responsive to the actuation of the various limit switches and other conventional control elements to operate the machine as described hereinafter. As the construction and operation of the control system does not form part of this invention it is not shown or described in detail. OPERATION T heoperation of the machine will first be described with reference to FIGS. 4 to 8.

Initially, a first tube T1 is supported on the mandrel close to the spindle nose 18 at one end but terminating short of the intermediate support 17 at the other. A second tube T2 extends through the support 17 and has its ends supported by the head 20 and on the end of the mandrel 15. A strip of metal S has been passed cold through the strip guide 21 and welded to the tube T1 at its end nearer the headstock, before the commencement of operation.

To complete the finning of tube T1, the motor 4 is started and the mandrel and leadscrew rotate. The saddle is moved by the leadscrew along the length of the tube T1 and rotation of the latter draws strip through the strip guide forming a helical fin F as shown in FIG. 4. The strip guide prevents wrinkling and buckling of the strip, and ensures that it is applied to the tube with the proper pitch. The fin is in no way secured to the tube throughout the greater part of its length but is held in place by being slightly indented into the metal of the tube as a result of the tension applied to the strip in the strip guide.

Just before the saddle reaches the meeting point of the two tubes, the finger 108 contacts and closes the switch 106. The control system 9 operates in response to such closure to pressurise the cylinder 105 and displace the slide 91 towards the tube so that the guillotine 100 and welding torch 104 occupy the positions shown in FIG. 5. That is, the guillotine blades embrace the fin but remain open while the electrode of the welding torch is disposed in the vertical plane including the axis of the mandrel as seen in FIG. 6. The cylinder 108 is pressurised and the torch is moved along the line 109 in FIG. 6, so as to bring the electrode into the broken line position 104a shown in that Figure. At the same time, the drive is changed over from motor 4 to motor 3 so that the mandrel is driven at a slower speed suitable for welding. The operation of the welder is so timed that the fin is welded to the adjacent ends of both tubes by a single line of welding. The finger 101 cooperates with the junction between the tube and fin and the torch follows the movements which the finger performs. The second limit switch 107 is then actuated and the drive to the mandrel (and leadscrew) disconnected and the cylinder 93 momentarily pressurised to operate the guillotine as seen in FIG. 7. This operation is so timed that the fin is severed at the meeting point between the two tubes. The welding torch slide and the cross slide are then retracted.

Finning of the tube T1 is now completed and the control system 9 operates cylinder 12 to retract the mandrel so that tube T1 can be removed. The cylinder 12 is then operated to return the mandrel which passes into the end of tube T2 which in the absence of the mandrel remained supported in the intermediate support 17. The saddle is then returned to its start position and brings with it the tube T2 which is drawn through the support fully on to the mandrel. The head is retracted and a further tube T3 placed on the cradles 203 between the support 17 and the head 20. The head 20 is then advanced to lift the fresh tube from the cradles and feed it into the position originally occupied by tube T2.

The situation is again that described originally with tube T2 occupying the position of tube T1 and with a fin already welded to it at one end. The control system then re-starts high speed motor 4 and finning then continues. When the weld between the fin and the tube T2 and the tube T3 is made, and the fin is severed, the finning of the tube T2 has been completed.

During the winding operation, the function of the strip guide 21 is to exercise control over the strip as bending takes place and to ensure that the strip is fed to the tube at the correct pitch, such control of the strip being particularly important as the strip is bent around the end radii of an oval tube, for example. As can be seen from FIG. 3, the strip guide is in the form of a block having a base section 22 and a head section 23. The base and head sections meet in a curved'surface 24 which has substantially the same curvature as the part of the tube of smaller radius. A guide slot 25 extends obliquely across the surface 24 and determines the path followed by the strip during winding.

In a practical embodimeht, the machine may be required to wind onto an oval tube having end radii of about 0.5 inches (1.27 cm) a strip of metal having a thickness of about 0.05 inches (0.127 cm) and a width of about 0.75 inches (1.87 cm).

In the stages of winding shown in FIGS. 9 to 11, the mandrel rotates and the strip S is drawn cold from the reel through the slot 25 which holds the strip tightly to the tube and so controls it that wrinkling and buckling are prevented. In particular such control takes place both in the bending zone 26 and in an ironing zone 27. The guide block is resiliently pressed against the mandrel by pneumatic or hydraulic cylinders, or by mechanical means such as springs or dead weights, such means being diagrammatically indicated in FIG. 8, where the piston rods 29, 30 of pneumatic cylinders are shown to act on the guide support.

During rotation of the mandrel, the guide block moves vertically and horizontally to ensure that at least the bending and ironing zones of the slot 25 are maintained close to or in contact with the tube. In addition, the guide block rotates about its vertical axis so that the pitch of the fin is controlled according to the radius of the tube at thatinstant being wound. After one end radius R1 has been finned as shown in FIGS. 9 and 10, strip is laid across the straight or large radius section which follows it R2, tight control of the strip during this stage being less essential. As shown in FIG. 1 1, the strip partially lifts out of the slot along part of its length between the bending and ironing zones 26, 27. After the stage shown in FIG. 11 is completed the guide, block moves downwards and to the left while providing close control during bending until the position shown in FIG. 8 is again reached. Depending on the difference between the major andminor dimensions of the tube, whether it be oval, eliptical, based on an oblong or a square with radiused corners based on a lobed figure with radiused corners, or any regular or irregular polygon, then, taking into account the height of the fin it is possible in certain cases to lock the slide 87 in one position is the slideway 86 and also to lock the guide 21 in one position on top of the slide 87, and means for locking the parts in these relative positions are provided but not shown in the drawing.

The guide block shown is illustrated diagrammat: ically and is not to be taken as the actual shape which will perform most satisfactorily in any given set of circumstances. The optimum shape and construction and the depth of the slot at various points must be determined by experiment.

In order to reduce the effect of the tube hitting against the base section 22 as the tube moves into its FIG. 11 position, it may be preferable for the base section to be cut away as shown at 28 in FIG. 9. Alternatively, the guide block may be in the form of a ring completely surrounding the tube so that during the stage shown in FIG. 9, the die is supported on the mandrel against the loading applied to the fin. Control in the ironing zone may then be obtained by the use of a guide separate from the main guide. Guides of other shapes may prove suitable or desirable depending on conditions.

in an alternative embodiment, not illustrated, the ironing zone is constituted by a pair of rollers, possibly conical rollers, associated with mechanism for maintaining them in close proximity to the tube surface. Possibly rollers may also, or instead, be used to achieve control in the bending zone. In a machine of different construction, instead of providing for movement of the guide block it is possible for the mandrel to swing so as to maintain the position of the guide relative to the mandrel.

It will be appreciated that numerous modifications may be made to the embodiment described by, for example, replacing parts of the guide block with movable fingers or rollers. Also the shape of the guide block may be changed, and the guide slot may be made adjustable in width. The configuration, construction and actual operation of the guide is therefore not material to this aspect of the invention, the essential feature of which is the guiding of the strip over a sufficient portion of its length as it is wound onto the tube such that rippling buckling, wrinkling and leaning are prevented.

In the foregoing, it has been assumed that the tube is non-circular. Firming of a circular tube presents a proposition which is a good deal simpler since the guide block can be replaced by a stationary block bolted to the bush housing, the block surrounding the tube and being provided with the necessary channel for reception of the strip.

Numerous modifications to the machine described provided to unload and reload the machine so that its operation is fully automatic. Similarly, although the apparatus provided by the invention is particularly intended for the finning of tubes, it is to be understood that solid shafts may also be finned by means of the apparatus providing that supports are provided to hold the shafts in position.

I claim:

1. A machine for winding a continuous fin onto tubing, comprising a frame including a headstock, a mandrel for supporting a first tube in a position relative to the frame, said mandrel extending through the headstock, means for withdrawing the mandrel at least partially through the headstock, a tailstock supported by the frame at a position remote from the headstock, an intermediate support supported by the frame at a position between the headstock and the tailstock, a tube support head associated with the tailstock, said tube support head and said intermediate support being adapted to support a second tube coaxially aligned with the first tube, means on the tailstock for advancing the tube support head towards the headstock to bring the second tube into coaxial alignment with the first tube, means for rotating the first and second tubes, a carriage mounting a strip guide and being movable along the frame longitudinally of the first tube and an end portion of the second tube, the combined efi'ect of rotation of the tubes and said longitudinal movement of the carriage resulting in strip fed through the strip guide being wound into a helical fin on the first tube and an end portion of the second tube, welding means for securing the fin to the first tube and the second tube, and severing means for severing the fin adjacent that end of the first tube remote fromthe head stock.

2. A machine as claimed in claim 1, wherein said welding means and said severing means are on said carriage.

3. A machine as claimed in claim 1, wherein said carriage supports a slide movable in a direction normal to the axes of the tubes, and said severing means and welding means are mounted on the slide.

4. A machine for winding metal strip into a continuous fin on tubing comprising:

a. a bed having slideways extending therealong for guiding a carriage for movement longitudinally of the bed;-

b. a headstock at one end of said bed;

0. a mandrel extending through said headstock;

d. mandrel support means movable away from said headstock thereby to retract the mandrel through the headstock;

e. a tailstock;

f. a tube support head;

g. means on said tailstock for advancing said support head towards the headstock; h. an intermediate support mounted on said bed, said intermediate support being so positioned relative to the headstock and tailstock that a first tube may be located between tne headstock and intermediate support but terminate short of the latter and that a second tube may be located between the intermediate support and support head when the latter is in its retracted position; the stroke of the means on said tailstock being such that said second tube so located is brought into abutment with the first tube on actuation of said means;

i. a strip guide on said carriage,

j. a cross slide on said carriage, said slide being movable between an operative position close to said mandrel and an inoperative position spaced from said mandrel;

k. a guillotine on said cross slide, said guillotine having blades positioned to embrace a fin on the tube when said slide is in its operative position; welding means and a slide therefor, said welding means slide being mounted to said cross slide such that said welding means is movable along a line inclined at an angle to the horizontal, said line being so positioned that when said cross-slide is in its opline intersect; in control means operable;

i. to advance the cross slide to its operative position as the strip guide nears the meeting point of the two tubes;

ii. to move said welding means along said line into position for effecting a weld between the strip and said tubes as said strip guide winds strip off one tube and on to the other,

iii. to operate said guillotine to sever the strip at said meeting point,

iv. to retract the mandrel to permit removal of the first tube,

v. to return the carriage and with it the second tube,

vi. to actuate the means on the tailstock so as to advance a third tube into contact with the second tube.

erative position the axis of the mandrel and said.

5. A machine for winding a continuous fin onto tubing comprising a frame, means for supporting a tube in position relative to the frame, means for rotating the tube, a carriage mounting a strip guide and being movable longitudinally of the tube, the combined effect of such movement and of the rotation of the tube resulting in strip being drawn through the strip guide to form a fin on the tube, a slide movable towards and away from the axis of the tube, a guillotine supported on said slide, said guillotine having cutting blades opening towards said tube, a welding means supported on said slide and movable relative to said slide along a predetermined path between an inoperative position and an operative position, and means operable on said carriage being moved longitudinally of the tube to a predetermined position relative to the end of the tube to advance said slide towards said tube into a position wherein the path of movement of said welding means intersects the line of contact between the strip and the tube, to move said welding means along said path to effect a weld, and to operate the guillotine to sever the strip.

6. A machine as claimed in claim 5, wherein said tube to be finned is in cross-section non-circular but devoid of sharp corners, and wherein said strip guide includes means for controlling the strip in respective bending and ironing zones, said last named means being resiliently urged into contact with the tube and being movable against such resilient force so as to follow movement of the surface of the non-circular tube.

7. A machine as claimed in claim 5, wherein said tube to be finned is non-circular, and said guide comprises a guide block having a surface shaped to abut the tube and to closely embrace the zone of smallest radii thereof, a guide slot extending obliquely across said surface, and support means for the guide block permitting rotation of the guide block and movement of the guide block in two directions normal to the tube axis.

8. A machine as claimed in claim 5, wherein said welding means for securing the fin to the tube is operative to weld the strip to the tube solely in the regions at the tube ends and the strip guide is effective to apply sufficient tension to the strip to indent the strip into the wall of the tube to thereby ensure its location in the region inbetween the tube ends.

9. A machine as claimed in claim 5, including a finger movable with the welding means and adapted to make contact with the tube and fin and to ensure proper positioning of the welding means during welding.

10. A machine as claimed in claim 5, including means for supporting a second tube in axially aligned abutting relationship with the first-mentioned tube, said welding means being maintained in the welding position while the carriage moves along an end portion of the second tube, operation of said guillotine being arranged to take place after welding of the strip to the second tube has been carried out.

11. In a machine for winding a continuous fin onto tubing, comprising a frame, means for supporting a first tube in position relative to said frame, means for rotating the tube, a carriage movable longitudinally of the tube from an initial position relative to the frame, a strip guide on the carriage and means for securing to the tube a fin wound thereon by the combined effect of rotation of the tube and longitudinal movement of the carriage, the improvement consisting in the provision of means for supporting a second tube in axially aligned relationship with the first-mentioned tube, said carriage being adapted at the end of longitudinal movement relative to the first tube to move longitudinally along part of the length of the second tube so that fin is wound onto an end portion of the second tube, said securing means being adapted to secure the fin to both tubes, and means for severing the fin adjacent the meeting point of the two tubes to separate the two tubes.

12. A machine as claimed in claim 11, including means for returning the carriage to its initial position at a high speed, thereby to bring the second tube into the position previously occupied by the first tube.

13. A machine as claimed in claim 11, wherein the securing means and the severing means are supported on the carriage.

14. A machine as claimed in claim 11, including a mandrel for supporting the first tube, the mandrel being of sufficient length to project from the end of the first tube into an end portion of the second tube.

15. A machine as claimed in claim 14, wherein the mandrel is retractable to release the first tube after said fin has been severed.

16. A machine as claimed in claim 11, including supports for a freshly positioned second tube, and a support head movable to lift the second tube from the supports and position it in said axially aligned relationship abutting said first tube.

17. A machine as claimed in claim 11, wherein said securing means is operative to secure the fin to the two tubes solely at the meeting end portions thereof.

18. A machine as claimed in claim 17, including means for driving said carriage at a slow speed during operation of said securing means.

19. A machine for winding a continuous fin onto oval tubing, comprising a frame, means for supporting an oval tube relative to the frame and for rotating the tube, a carriage movable longitudinally of the tube, and a strip guide supported by the carriage, said strip guide comprising a guide block having a surface shaped to correspond with the surface of the tube at least in the zone thereof of smallest radii, a guide slot extending obliquely across the surface, and support means permitting the guide block to move in two directions normal to the tube axis so as to maintain said surface in contact with the tube as the latter rotates and permitting the guide block to rotate about an axis normal to the tube axis to ensure that the pitch of the fin is controlled according to the radius of that zone of the tube being wound at any instant.

20. A machine as claimed in claim 19, wherein the carriage supports a welding means associated with a finger arranged to follow the line where the fin meets the tube and to control the position of the welding means.

21. A machine for winding a continuous fin onto tubing, comprising a frame, a mandrel for supporting a tube in position relative to said frame, means for rotating the tube, a carriage movable longitudinally of the tube, a strip guide on the carriage, metal strip being arranged to pass through said strip guide and be wound into a helical fin on the tube as the carriage moves longitudinally of the tube, said strip guide being adapted to tension the strip as it passes through the guide sufficiently to cause the strip to be indented into the tube wall and thereby to be located, and welding means on the carriage operable to weld the fin to the tube in the regions of the tube ends. 

1. A machine for winding a continuous fin onto tubing, comprising a frame including a headstock, a mandrel for supporting a first tube in a position relative to the frame, said mandrel extending through the headstock, means for withdrawing the mandrel at least partially through the headstock, a tailstock supported by the frame at a position remote from the headstock, an intermediate support supported by the frame at a position between the headstock and the tailstock, a tube support head associated with the tailstock, said tube support head and said intermediate support being adapted to support a second tube coaxially aligned with the first tube, means on the tailstock for advancing the tube support head towards the headstock to bring the second tube into coaxial alignment with the first tube, means for rotating the first and second tubes, a carriage mounting a strip guide and being movable along the frame longitudinally of the first tube and an end portion of the second tube, the combined effect of rotation of the tubes and said longitudinal movement of the carriage resulting in strip fed through the strip guide being wound into a helical fin on the first tube and an end portion of the second tube, welding means for securing the fin to the first tube and the second tube, and severing means for severing the fin adjacent that end of the first tube remote from the head stock.
 2. A machine as claimed in claim 1, wherein said welding means and said severing means are on said carriage.
 3. A machine as claimed in claim 1, wherein said carriage supports a slide movable in a direction normal to the axes of the tubes, and said severing means and welding means are mounted on the slide.
 4. A machine for winding metal strip into a continuous fin on tubing comprising: a. a bed having slideways extending therealong for guiding a carriage for movement longitudinally of the bed; b. a headstock at one end of said bed; c. a mandrel extending through said headstock; d. mandrel support means movable away from said headstock thereby to retract the mandrel through the headstock; e. a tailstock; f. a tube support head; g. means on said tailstock for advancing said support head towards the headstock; h. an intermediate support mounted on said bed, said intermediate support being so positioned relative to the headstock and tailstock that a first tube may be located between tne headstock and intermediate support but terminate short of the latter and that a second tube may be located between the intermediate support and support head when the latter is in its retracted position; the stroke of the means on said tailstock being such that said second tube so located is brought into abutment with the first tube on actuation of said means; i. a strip guide on said carriage, j. a cross slide on said carriage, said slide being movable between an operative position close to said mandrel and an inoperative position spaced from said mandrel; k. a guillotine on said cross slide, said guillotine having blades positioned to embrace a fin on the tube when said slide is in its operative position; l welding means and a slide therefor, said welding means slide being mounted to said cross slide such that said welding means is movable along a line inclined at an angle to the horizontal, said line being so positioned that when said cross-slide is in its operative position the axis of the mandrel and said line intersect; m control means operable; i. to advance the cross slide to its operative position as the strip guide nears the meeting point of the two tubes; ii. to move said welding means along said line into position for effecting a weld between the strip and said tubes as said strip guide winds strip off one tube and on to the other, iii. to operate said guillotine to sever the strip at said meeting point, iv. to retract the mandrel to Permit removal of the first tube, v. to return the carriage and with it the second tube, vi. to actuate the means on the tailstock so as to advance a third tube into contact with the second tube.
 5. A machine for winding a continuous fin onto tubing comprising a frame, means for supporting a tube in position relative to the frame, means for rotating the tube, a carriage mounting a strip guide and being movable longitudinally of the tube, the combined effect of such movement and of the rotation of the tube resulting in strip being drawn through the strip guide to form a fin on the tube, a slide movable towards and away from the axis of the tube, a guillotine supported on said slide, said guillotine having cutting blades opening towards said tube, a welding means supported on said slide and movable relative to said slide along a predetermined path between an inoperative position and an operative position, and means operable on said carriage being moved longitudinally of the tube to a predetermined position relative to the end of the tube to advance said slide towards said tube into a position wherein the path of movement of said welding means intersects the line of contact between the strip and the tube, to move said welding means along said path to effect a weld, and to operate the guillotine to sever the strip.
 6. A machine as claimed in claim 5, wherein said tube to be finned is in cross-section non-circular but devoid of sharp corners, and wherein said strip guide includes means for controlling the strip in respective bending and ironing zones, said last named means being resiliently urged into contact with the tube and being movable against such resilient force so as to follow movement of the surface of the non-circular tube.
 7. A machine as claimed in claim 5, wherein said tube to be finned is non-circular, and said guide comprises a guide block having a surface shaped to abut the tube and to closely embrace the zone of smallest radii thereof, a guide slot extending obliquely across said surface, and support means for the guide block permitting rotation of the guide block and movement of the guide block in two directions normal to the tube axis.
 8. A machine as claimed in claim 5, wherein said welding means for securing the fin to the tube is operative to weld the strip to the tube solely in the regions at the tube ends and the strip guide is effective to apply sufficient tension to the strip to indent the strip into the wall of the tube to thereby ensure its location in the region inbetween the tube ends.
 9. A machine as claimed in claim 5, including a finger movable with the welding means and adapted to make contact with the tube and fin and to ensure proper positioning of the welding means during welding.
 10. A machine as claimed in claim 5, including means for supporting a second tube in axially aligned abutting relationship with the first-mentioned tube, said welding means being maintained in the welding position while the carriage moves along an end portion of the second tube, operation of said guillotine being arranged to take place after welding of the strip to the second tube has been carried out.
 11. In a machine for winding a continuous fin onto tubing, comprising a frame, means for supporting a first tube in position relative to said frame, means for rotating the tube, a carriage movable longitudinally of the tube from an initial position relative to the frame, a strip guide on the carriage and means for securing to the tube a fin wound thereon by the combined effect of rotation of the tube and longitudinal movement of the carriage, the improvement consisting in the provision of means for supporting a second tube in axially aligned relationship with the first-mentioned tube, said carriage being adapted at the end of longitudinal movement relative to the first tube to move longitudinally along part of the length of the second tube so that fin is wound onto an end portion of the second tube, said securing means being adapted to secure thE fin to both tubes, and means for severing the fin adjacent the meeting point of the two tubes to separate the two tubes.
 12. A machine as claimed in claim 11, including means for returning the carriage to its initial position at a high speed, thereby to bring the second tube into the position previously occupied by the first tube.
 13. A machine as claimed in claim 11, wherein the securing means and the severing means are supported on the carriage.
 14. A machine as claimed in claim 11, including a mandrel for supporting the first tube, the mandrel being of sufficient length to project from the end of the first tube into an end portion of the second tube.
 15. A machine as claimed in claim 14, wherein the mandrel is retractable to release the first tube after said fin has been severed.
 16. A machine as claimed in claim 11, including supports for a freshly positioned second tube, and a support head movable to lift the second tube from the supports and position it in said axially aligned relationship abutting said first tube.
 17. A machine as claimed in claim 11, wherein said securing means is operative to secure the fin to the two tubes solely at the meeting end portions thereof.
 18. A machine as claimed in claim 17, including means for driving said carriage at a slow speed during operation of said securing means.
 19. A machine for winding a continuous fin onto oval tubing, comprising a frame, means for supporting an oval tube relative to the frame and for rotating the tube, a carriage movable longitudinally of the tube, and a strip guide supported by the carriage, said strip guide comprising a guide block having a surface shaped to correspond with the surface of the tube at least in the zone thereof of smallest radii, a guide slot extending obliquely across the surface, and support means permitting the guide block to move in two directions normal to the tube axis so as to maintain said surface in contact with the tube as the latter rotates and permitting the guide block to rotate about an axis normal to the tube axis to ensure that the pitch of the fin is controlled according to the radius of that zone of the tube being wound at any instant.
 20. A machine as claimed in claim 19, wherein the carriage supports a welding means associated with a finger arranged to follow the line where the fin meets the tube and to control the position of the welding means.
 21. A machine for winding a continuous fin onto tubing, comprising a frame, a mandrel for supporting a tube in position relative to said frame, means for rotating the tube, a carriage movable longitudinally of the tube, a strip guide on the carriage, metal strip being arranged to pass through said strip guide and be wound into a helical fin on the tube as the carriage moves longitudinally of the tube, said strip guide being adapted to tension the strip as it passes through the guide sufficiently to cause the strip to be indented into the tube wall and thereby to be located, and welding means on the carriage operable to weld the fin to the tube in the regions of the tube ends. 